It is known that submarines need to be provided with equipment such as sensors and the like, located at the free top-end of shafts which are raised when the submarine is at the periscope level and are made to retract into their own housing for a normal submerged operation.
Such housings obviously have a top opening which should be sealed by means of a hatch including either a single part or two parts, so as not to alter the hydrodynamic configuration of the structure of the submarine and at the same time to reduce the noise caused by vortices during normal submerged operation.
There are also known engineering solutions based on the use of independent actuating devices of hydraulic, pneumatic or electrical types capable of regulating independently the sequence of opening--outward movement--retraction and closure of the shaft and hatch. Such independence, however, requires that such devices be provided with means of control and regulation designed to prevent any error in such sequence, which error could cause interference between the shaft and hatch resulting in damage to the various parts.
Such means of control however, in addition to entailing higher costs and regular preventive maintenance to ensure the efficiency thereof, do not guarantee, because of their independence, efficient and reliable direct control of the aforedescribed sequence.